The present invention relates to a date recording and reproducing apparatus of a helical scanning system, and more particularly to tracking control using a control signal.
In a data recording and reproducing apparatus of a helical scanning system, when there is a difference (that is, a tracking error) between a recording track (hereinafter referred to as an information track) of a video signal on a magnetic tape and a scanning locus of a reproducing magnetic head, a reproduced signal is not obtained with satisfactory quality and accordingly it is necessary to perform tracking control so as to remove the tracking error.
For example, a conventional data recording and reproducing apparatus of a helical scanning system performs the so-called capstan servo tracking control in which a control signal is recorded on the magnetic tape in the longitudinal direction thereof in a manner corresponding to the information track and is reproduced by a fixed control head so that the tracking error is detected from a variation in a phase of the reproduced control signal to control a rotational phase of a capstan motor for moving the magnetic tape at a fixed speed.
However, since the control signal recorded in the longitudinal direction of the magnetic tape is recorded by a control head which is different from the rotary magnetic head recording and reproducing the video signal, the video signal can not optimally be reproduced due to a difference in the relation between the recorded position of the control signal and the position of the information track on the magnetic tape. One of the reasons thereof is that the relation of mounting positions of the control head and the rotary magnetic head is slightly different depending on each data recording and reproducing apparatus. Consequently, a distance (hereinafter referred to as an X value) between the recorded position of the control signal and a record starting position of the information track corresponding to the recorded position of the control signal is slightly different depending on each data recording and reproducing apparatus. Accordingly, when a signal recorded on a magnetic tape by a data recording and reproducing apparatus is reproduced by a different data recording and reproducing apparatus, the tracking error is increased and optimum reproduction is often impossible.
Heretofore, in order to reduce such a tracking error to be as small as possible, the tracking adjustment is made upon reproduction by the data recording and reproducing apparatus to thereby vary a phase control timing of the capstan, so that a difference in the relation of the recorded positions of the control signal and the information track is corrected. As another tracking adjustment method, a method of making an automatic tracking adjustment is known to maximize a level of a reproduced video signal.
Further, as another example, an automatic tracking control method using a wobbling method is known in which a rotary magnetic head is attached on a bimorph plate and the rotary magnetic head is position-controlled upon the reproduction so that a reproduced video signal is obtained with a maximum level while a very small vibration is given to the rotary magnetic head by the bimorph plate.
As the prior arts described above, there is an example as disclosed in Japanese Patent Document No. JP-A-57-198566, for example.